Due to G 89 02 562.8 an ultra sound welding device for fixing wire ends of wire windings at terminal lugs of a commutator became known. Thereby a sonotrode of the ultra sound welding device presses the wire against a terminal lug of the commutator. Thereby ultra sound energy is directly inserted into the wire, which warms up so much that it creates a welding connection with the terminal lug of the commutator. Such an ultra welding procedure has the disadvantage that the material of the wire and the terminal lug are selectively melted in order to create a strong connection. Such a strong heat input can cause a damaging of the components that are adjoining the terminal lug.